I. Field
The present disclosure relates generally to electronics, and more specifically to filters for a wireless device.
II. Background
A wireless device (e.g., a cellular phone or a smartphone) in a wireless communication system may transmit and receive data for two-way communication. The wireless device may include a transmitter for data transmission and a receiver for data reception. For data transmission, the transmitter may modulate a radio frequency (RF) carrier signal with data to obtain a modulated RF signal, amplify the modulated RF signal to obtain an output RF signal having the proper transmit power level, and transmit the output RF signal via an antenna to a base station. For data reception, the receiver may obtain a received RF signal via the antenna and may condition and process the received RF signal to recover data sent by the base station.
A wireless device may be required to meet various performance requirements. For example, a transmitter within the wireless device may be required to meet stringent harmonic rejection requirements at an antenna connector, which means that harmonics of an output RF signal should be below a specified level. A large portion of the transmitter may be implemented on an integrated circuit (IC) chip, and it may be challenging to achieve the required level of harmonic rejection on-chip. Hence, passive circuit components such as inductor and capacitor (LC) traps and/or diplexers may be placed on a printed circuit board (PCB) at or near the antenna connector to reduce the harmonic level. However, the LC traps and/or diplexers would increase the size and cost of the wireless device. Furthermore, the wireless device may support many frequency bands and may require harmonic traps for different bands and/or different harmonics of each band. A large number of circuit components may be needed to implement all of the required harmonic traps on the PCB, which may greatly increase the size and cost of the wireless device.